1. Field of the Invention
The invention relates to solar energy conversion arrays and more particularly to an integrated array of cadmium sulfide-copper sulfide photovoltaic cells connected in a series circuit relationship.
2. Description of the Prior Art
One example of a prior art array of photovoltaic cells is disclosed in U.S. Pat. No. 4,042,418, issued to William J. Biter on Aug. 16, 1977 and assigned to the same assignee as this application. This patent discloses two embodiments of an integrated array of photovoltaic cells. In the first embodiment, illustrated in FIG. 2 of the Biter patent, the negative electrode of each of the cells of the array is formed on an insulating substrate by depositing thereon a grid of electrically conductive members. The substrate and the grid are then covered by a layer of N conductivity type semiconductor material such as cadmium sulfide. A layer of P conductivity type copper sulfide is formed on the upper surface of the cadmium sulfide by dipping the cadmium sulfide layer in a solution containing cuprous ions or by vapor deposition. A second grid of electrically conducting strips, with each of these strips forming the positive electrode of a cell, is then deposited on the upper layer of the copper sulfide. Current collector grids are affixed to the P conductivity copper sulfide layer in the areas between the positive electrodes. Each of the current collector grids overlaps and is in sole electrical contact with an adjacent positive electrode. The positive electrode of each cell overlies the edge of the negative electrode of an adjacent cell. A low electrical resistance connection between the positive and negative electrodes of adjacent cells of the array is made through the semiconductor layer to couple all of the cells of the array in series circuit relationship.
In a second embodiment, illustrated in FIG. 3 of the Biter patent, portions of the copper sulfide layer are removed to expose regions of cadmium sulfide. A second grid forming the positive electrodes of the array is deposited on the exposed regions of cadmium sulfide. This permits the positive and negative electrodes of adjacent cells to be connected through the thin cadmium sulfide layer alone.